Characteristics and Prognosis of Patients with Immunoglobulin M Monoclonal Gammopathy.

Many patients with immunoglobulin M (IgM) monoclonal gammopathy remain asymptomatic and, consequently, untreated; however, few studies have evaluated the clinical course and prognosis of these patients. Using the screening procedures at our hospital, 74 patients with IgM monoclonal gammopathy were selected. We excluded 11 patients in whom the treatment for lymphoid neoplasms had been initiated at the time of IgM monoclonal protein detection. The remaining 63 patients were considered to be the patient population with IgM MGUS and asymptomatic WM, and were analyzed. In these patients, the median overall survival was longer than 14 years. More than half of these patients died from causes other than lymphoid neoplasm. The cumulative incidence of lymphoid neoplasm requiring treatment was 17.5%. In five of eight patients requiring treatment for lymphoid neoplasms, the causes of death were related with these lymphoid neoplasms. Our study suggests that not all patients with IgM monoclonal gammopathy require uniform treatment for prolonged survival; however, most lymphoid neoplasms requiring treatment are refractory diseases. Our findings may help manage patients with macroglobulinemia.